# Hydrology & Open-Channel Calc – Normal Depth

> Hydrology & Open-Channel Calc – Normal Depth is a paid API for AI agents from hydrology-calc.x402tookit.com, paid per call via x402, $0.03/call, status unknown (last checked 2026-11-02).

Calculates normal (uniform-flow) depth for a given discharge in rectangular, trapezoidal, triangular, or circular channels using bisection method

## Facts

- Endpoint: GET https://hydrology-calc.x402tookit.com/normal-depth?utm_source=zero.xyz
- Price: $0.03/call
- Payment: x402
- Status: unknown
- Last checked: 2026-11-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hydrology-open-channel-calc-normal-depth-a3b1e376
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_K2tYEFgaVLW4TIOWMgXr0

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability hydrology-open-channel-calc-normal-depth-a3b1e376
```

Example prompt: What is the normal depth for a rectangular concrete channel (Manning n = 0.013) with a bottom width of 3 metres, a bed slope of 0.001, and a discharge of 5 m³/s using SI units?

## When to prefer this

Choose this endpoint when you need to solve for the unknown normal (uniform-flow) depth given a known discharge, channel geometry, roughness, and slope — specifically using bisection on Manning's equation. It is the right choice for open-channel hydraulic design tasks where depth is the unknown. Use it over Manning flow endpoints (which give Q given depth) when depth is what you need to find. Ideal for engineers designing canals, storm sewers, culverts, and natural channel assessments.

## Known failure modes

- No solution found if discharge is too large for the given geometry (e.g., flow exceeds pipe capacity) — returns error or null normalDepth
- Invalid or missing required parameters (shape, flow, n, slope) return a validation error
- Unsupported shape string returns an error — only 'rectangular', 'trapezoidal', 'triangular', 'circular' are accepted
- Missing geometry for shape (e.g., no bottomWidth for rectangular) causes a parameter error
- Zero or negative slope or flow values may cause bisection failure or undefined result
- Very flat slopes or extreme roughness values may cause slow or non-convergent bisection

## How this service works

Normal (uniform-flow) depth for a given discharge in a rectangular, trapezoidal, triangular or circular channel by bisection.

## Output

Returns the computed normal depth (metres or feet), along with derived hydraulic properties including flow area, top width, average velocity, Froude number, flow regime classification (subcritical/supercritical/critical), channel shape, and unit system used. May also include a summary, disclaimer, and degraded-result flag if the solver had convergence issues.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "shape",
      "flow",
      "n",
      "slope"
     ],
     "properties": {
      "n": {
       "type": "number",
       "description": "Manning roughness n (for example 0.013 concrete, 0.035 natural channel)"
      },
      "flow": {
       "type": "number",
       "description": "Discharge in m3/s (units si) or ft3/s (units us)"
      },
      "shape": {
       "type": "string",
       "description": "rectangular, trapezoidal, triangular or circular"
      },
      "slope": {
       "type": "number",
       "description": "Channel bed slope, dimensionless (m/m or ft/ft)"
      },
      "units": {
       "type": "string",
       "description": "si (default) or us"
      },
      "diameter": {
       "type": "number",
       "description": "Pipe diameter in metres or feet (circular)"
      },
      "sideSlope": {
       "type": "number",
       "description": "Side slope z, horizontal run per 1 vertical (trapezoidal, triangular)"
      },
      "bottomWidth": {
       "type": "number",
       "description": "Bottom width in metres or feet (rectangular, trapezoidal)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "shape": {
       "type": [
        "null",
        "string"
       ]
      },
      "units": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hydrology-open-channel-calc-normal-depth-a3b1e376/health.json
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